THE engineering problems in designing a vehicle and a power plant to carry men into space are formidable. They are matched by the problems involved in what
might be called the housekeeping aspects of space travel.

To keep the crew of a spaceship fed and in good physical and mental health will
require the development of wholly new techniques in many fields. This is
particularly true of vehicles that are to make long voyages to other
planets -- or to leave our solar system entirely.

WEIGHTLESSNESS. Whenever the propulsion system is turned off, the crew and
everything else aboard the space vehicle will be completely without weight.
Although individuals have undergone very short periods of gravity loss without
apparent ill effects, we still know very little about what this phenomenon will
mean in space travel. Certainly many common movements will become difficult.
Gravity plays a considerable part in the mechanism by which the individual
perceives his body's position in space. With gravity removed, the eyes will
have to take over this function.

OXYGEN SUPPLY. Every crewman will require 500 liters of oxygen every 24
hours -- too much to be carried on any but the shortest trips. Since plants
release oxygen, one answer might be to carry along a batch of the tiny
water-borne plants called algae: 2.3 kilograms of Alga Chlorella pyrenoidosa
produce enough oxygen to supply one man. Plants require light energy for
carrying out their metabolic processes, however; so artificial sources of
radiant energy will have to be carried aboard the vehicle for flights outside
the solar system. This presumably will increase the demand on the vehicle's
power plant.

CARBON DIOXIDE DISPOSAL. With every breath man expels carbon dioxide, which
must be removed from the air within the vehicle. Since plants consume carbon
dioxide, the same algae might take care of this problem.

WATER VAPOR CONTROL. The crew will also release considerable water into the
atmosphere of the vehicle through their perspiration and breath. A humidity
control system will be needed to keep the vapor content of the air within the
limits of comfort.

WASTE PRODUCT DISPOSAL. The vehicle will be sealed so nothing can be expelled.
Human wastes will have to be treated by bacteria in a closed sewage system.

WATER SUPPLY. Water used for human or other purposes on the ship will have to
be recovered, cleaned, and reused over and over again.

FOOD. For a space voyage of any length the crew will have to produce their own
food as they go along. Here again the useful little algae offer one solution.
The same Chlorella pyrenoidosa is highly nutritious and can be made to produce
either a high concentration of fats or a high concentration of protein.

TEMPERATURE CONTROL. The cold in outer space will be intense, particularly
outside of the solar system. An insulation system of extreme efficiency will be
needed to minimize loss of heat through the vehicle's shell. Probably double
hulls, one within the other, will be required. Whatever heat is lost will have
to be replaced by a heating system.

LIGHT. Traveling within the solar system but outside the earth's atmosphere,
the crew will find everything in sunlight cruelly bright, everything in shadow
in inky darkness. The sharp contrast will present visual adaptation problems to
space travelers. At the same time they will have to be careful to avoid looking
directly at the sun for fear of retinal burn, since the sun is far more
dangerous when not filtered through the atmosphere. All observation ports will
have to be equipped with light filters.

DAY-NIGHT CYCLE. Since there will be no normal succession of day and night, the
crew will have to adjust to an artificial cycle for work, recreation, and
sleep. Laboratory experiments have shown that the body can adapt to a cycle
ranging from 18 to 28 hours.

COMPANIONSHIP. Choosing and matching the individuals who will make up the space
crews, which will be completely isolated from all other human contact for
months or years, will be a vital problem. Studies made by the armed forces for
selecting men for isolated outposts give some clues to possible approaches.
Groups of two have been found to develop extreme friction. Groups of four or
more tend to break up into two groups and again friction develops. Three-person
units are considered preferable since each individual is considerate of the
others lest they combine against him. Space crews might be broken up into three
groups of three individuals with rotation of individuals from group to group.